Food Health with Increased Probiotic Survival During Storage

Abstract

In recent years, due to the increasing concern of consumers about their food health. Pay attention to foods not only as a source of nutrients but also as promoters of health and wellness-hence the increase in demand for foods that have active or functional ingredients (especially natural ingredients). They increase nutritional value and nutritional health. Changes in food consumption, disorder the intestinal microbial system. Maintaining the health benefits of consuming beneficial bacteria that are present in the intestinal system. Probiotics are essential for improving intestinal microbial homeostasis. Probiotics are living microorganisms that, if recommended in sufficient quantities, can have positive effects on human health. Lowers cholesterol, improves lactose intolerance, increases nutritional value and prevents cancer. Probiotics are unstable during storage and the gastrointestinal tract (pH and bile salts). For this reason, the survival of probiotic cells and the absence of changes in the sensory properties of the product during storage are of have fundamental importance. Encapsulation and co-encapsulation with prebiotics are often a good way to increase the resistance of probiotic bacteria to difficult conditions and their survival. This leads to improved production of probiotic products and increased food health in the world.

1. Introduction

Probiotics are living microbes that must be in the number of 10⁶ log Cfu/gr at the time of entering the intestinal environment to have their beneficial effects on human health [1]. Probiotics are usually one or mixture of several microorganisms, when consumed by humans or animals, they have many beneficial effects on the body. Therefore, researchers are trying to add it to food the survival of probiotics. Since dairy products are Suitable for the transmission and survival of probiotic bacteria, most probiotic bacteria enter dairy products such as yogurt, Dough and various dairy desserts [2]. Due to the presence of animal cholesterol, lactose intolerance and sensitivity of some people to dairy products, it is necessary to study probiotic products with new flavors and non-dairy products, especially herbal [2]. Researchers are always looking for ways to improve the survival of probiotic bacteria to increase the survival of probiotics in Unfavorable environmental conditions, including during the production and storage of food products, as well as acidic and biliary conditions in the gastrointestinal tract [3, 4]. it is recommended that probiotic foods contain at least 108 log Cfu / gr at the time of consumption [1]. One of the newest methods that has had significant effects in this regard is the microencapsulation of bacteria in different ways by different coatings. From a microbiological point of view, microencapsulation is the monopoly of bacterial cells with hydrocolloid coatings that are used to separate and protect it from the external environment. The main purpose of microencapsulation is to increase the survival of bacterial cells during storage, passage and release in the gastrointestinal tract [5]. Symbiotic, on the other hand, are a mixture of probiotics and prebiotics that affect the health of the host, selectively stimulating probiotic growth. And activate, metabolize beneficial intestinal bacteria, thus improving beneficial effects on the host [5]. By adhering to intestinal epithelial cells, probiotics can improve micro biota and digestion. Provides protection against pathogens and carcinogenic properties [1]. In this chapter, a brief description of probiotics and their increase in survival in different ways are depicted.

2. Definition and role of probiotics

The word probiotic, meaning to live, is derived from the Greece language. For more than 4,000 years, lactic acid bacteria have been used to increase the shelf life of various foods through fermentation processes. In 1857, Pasteur discovered that microorganisms were responsible for fermenting milk and play role in the production of lactic acid, which was eliminated by boiling milk. The Clinton Processing Company (USA), for first in 1881, produced lactic acid by fermentation Process. The idea of ​​using one-way primer cultures in the decades 1940 and 1950 consisting of lactic acid bacteria was evolving and becoming commercially available [3]. Researchers have observed widespread in the decades 1980, use of lactic acid bacteria in biomedicine, food preservation, food processing, and fermentation and animal husbandry [3]. In 2002, the World Health Organization provided a comprehensive definition of probiotics: Probiotics are living microorganisms that, if taken in sufficient amounts, have beneficial effects on host health [6, 7].

The gastrointestinal tract contains millions of bacteria, the balance of which is very important for the gastrointestinal tract and the functioning of the immune system. During the day, the intestinal microflora is exposed to various stresses (use of antibiotics, anxiety and food poisoning). Which can create an imbalance between the so-called (good) and (bad) bacteria. However, eating foods that contain extra probiotics can increase the level of healthy or “good” bacteria in the gut which can change the microbial balance in this way [8]. Probiotics are classified as “safe” bacteria because their metabolism is saccharolytic. Probiotics are classified as “safe” bacteria because their metabolism is saccharolytic, (That is, they break down carbohydrates in the large intestine to produce short-chain fatty acids). This process is also known as fermentation and is beneficial to the host [8].

3. Selection criteria and requirements for probiotic strains

In the process of selecting probiotic strains for consumption, it must be approved by the WHO, FAO and the European Food Safety Authority (EFSA) for their safe status (GRAS) and (QPS) [4]. Recommended properties for a probiotic bacterium that have shown good and prominent effects on human health include [9]:

3.1 Having a safe status, probiotic bacteria

Bacterial lactic acid has been used to produce commercial probiotic products such as Lactobacillus casei and L. plantarum isolated from cheese and has shown good and prominent effects on human health [3].

3.2 Survive and have resistance to low pH and bile salts

Grosu-Tudor et al observed in Species (L. citreum, L. brevis, Leuconostoc mesenteroides, L. plantarum) isolated from fermented vegetables. have acceptable resistance in the presence of stomach acid and bile salts [3]. with the viability rates of 105 .10⁸ CFU/ml after 24 hours of incubation [3].

3.3 Ability to adhere to and colonize the gastrointestinal tract (GIT)

Adherence to intestinal surfaces is one of the most important criteria for selecting strong probiotic isolates. Some probiotic strains are isolated from fermented foods that have significant adhesion by producing intestinal mucosa. Such as Lactococcus lactis IS.16183, L. plantarum and Lactobacillus rhamnosus IS.7257 and inhibits the binding of Escherichia coli [3].

3.4 Ability to survival during storage and fermentation process in food

Probiotic products are usually recommended for storage in 4 to 5°C and should be used before the expiration date [3]. The criteria and requirements of probiotic strains are listed in detail in the Table 1 below:

Criteria	Required specifications
Immunomodulatory effects	Animal or human origin. Isolated from the gastrointestinal tract of healthy individuals. Accurate identification and matching (phenotype and genotype traits). Lack of relevant information related to infectious diseases. No side effects.
Function	Competing with intestinal bacteria. Ability to survive and maintain metabolic growth activity at the site. Resistant to bile salts and enzymes. Resistance to bile salt and low pH environment Antagonistic activity against pathogens (For example: Helicobacter pylori, Salmonella sp., Listeria monocytogenes, Clostridium
Technological capability	Easy production at high inoculation rates vSurvival and stability of probiotic bacteria during the process (freezing and freeze-drying under vacuum Preparation and distribution of probiotic products. Increase survival in final products (in aerobic and aerobic conditions) Ensure the optimal sensory properties of the final products Resistance to bacteriophages

Table 1.

Criteria for selection of probiotic species.

4. Strategies to improve the survival of probiotics in food products and the digestive system

Probiotics are now recognized as the top pragmatic food products, and these health benefits are enhanced by prebiotics and short-chain oligosaccharides; because these substances help increase the growth of beneficial bacteria in the intestinal tract [5]. Processing conditions in food products such as oxidation and temperature are important for the preservation and survival of bacterial cells. High temperatures during the survival process are harmful to microorganisms. Reduction of oxygen during fermentation plays an important role in the elimination of aerobic microorganisms. Storage conditions such as packaging such as moisture, oxygen, temperature should be appropriate. Microencapsulation techniques to protect bacterial cells cause high survival of these microorganisms in food products as well as in the gastrointestinal tract (low pH in gastric salt and bile in the small intestine) (Table 2) [5].

Food product	Compound added	Research Findings	References
Semi- hard cheese	Fructo- oligosaccharide	viability of probiotic strains	Langa el al., 2019
Wheat bread	Microbial polysaacharide- Pullalan	digestibility and fermentation of wheat bread samples	Nithyabalasundari et al., 2019
Yogurt	Chitoologosaccharide
Orange juice	Xylooligosaccharide	Preservation of chemical stability in ultrasound treatment	Eric et al., 2019
Edible starch film	Nystose	growth of probiotic organisms and formation of organic acids	Gabrielly et al., 2019
Fermented milk	Inulin	Improves the growth of lactic acid bacteria and improves sensory and physical properties	Ozturkuglu et al., 2019
Apple by-product	homogalacturonan and rhamnogalacturonan	Consumption of carbon source by probiotics and production of short chain fatty acids and increase the level of HDL in rats.	Inmaculada et al., 2020
Whole wheat grain flour	Arabinoxylan	increase the growth of intestinal microbiota and reduce the growth of pathogenic organisms	Candela et al., 2020
Stirred bio yogurt	Chickpea flour	Improves bacterial growth and our sensory, antioxidant and tissue properties	Hend et al., 2020
The Human Body	arabinoxylan and arabinoxylan oligosaccharides	Effected in adiposity reduction	Kerry et al., 2018
Green coffee spent	Mono- oligosaccharide with mannose and galactose	Stimulates the growth of Lactobacillus casei andLactobacillus fermentum, Resistance to stomach environment	Nivas et al., 2019

Table 2.

The effect of prebiotics on food.

5. Prebiotic

Probiotics are indigestible foods that are by beneficial bacteria and promote the growth and activity of probiotics in the gut, therefore probiotics can be used as functional foods. Prebiotics increase the body’s immune system by increasing intestinal microbial activity and the production of short-chain fatty acids [10]. The presence of prebiotics in the large intestine causes energy to be created by some bacteria during sugar consumption and fermentation. The most common hosts for prebiotics are Bifidobacterium bacteria and Lactobacillus. Which improves the growth of these two bacterial species and leads to the production of bacteriocins, which are a potential inhibitor of the growth of pathogenic bacteria [11]. Some of the prebiotics available in the inulin market are fructoo oligosaccharides (FOS) and galacto oligosaccharides (GOS), arabinoxylan [11]. Prebiotics can be obtained naturally from sources such as vegetables, fruits and grains. Prebiotics can reduce the incidence and duration of diarrhea, relieve inflammation, prevent colon cancer, and absorb minerals [11]. In a study by Anirban et al., Prebiotics such as fructoligosac (FOS) and inulin were used for stimulate the growth of Bifidobacterium in food [6]. The combination of probiotics and prebiotics leads to the formation of synbiotics. They increase the life and efficiency of probiotic bacteria in the intestine. Research has shown the effect of synbiotics on human health.

6. Effective level of probiotic microorganisms

In order of probiotic to survive, in the gastrointestinal tract, they must be able to tolerate low pH, gastric pepsin, bile salts, pancreatic, and the ability to attach to the intestinal mucosa [7, 8]. Probiotic survival in product is affected by various factors such as pH, acidity, hydrogen peroxide and storage temperature [12, 13]The efficiency of probiotic bacteria in the product depends on the dose, and their survival during storage, its survival in the intestinal environment [14]. Therefore, bacteria cannot survive due to unfavorable conditions during food processing and storage [15]. If probiotics survive, they will change the taste of the final product during storage [16]. Survival means the presence of at least a sufficient number of viable probiotic cells at the time of food consumption [17]. The general agreement on the recommended levels for the amount of probiotics in the product at the time of consumption should contain at least 10⁸ (CFU) / ml or gr [18]. The International Dairy Federation recommends that the minimum concentration of probiotics be around 10⁶.10⁷ CFU / ml at the end of the shelf life [10].

7. Common genera and species of probiotic microorganisms

Probiotic products may contain one or more selected microbial strains. Human probiotic microorganisms mostly belong to the genera Lactobacillus, Bifidobacterium, Lactococcus, Streptococcus and Enterococcus. In addition, gram-positive bacteria belonging to the genus Bacillus and some yeast species belonging to the genus Saccharomyces are commonly used in probiotic products. The largest group of lactic acid bacteria belongs to the genus Lactobacillus, which includes more than 50 different species. Lactic acid bacteria are gram-positive, spore-free, anaerobic fermentative bacteria that grow anaerobically and they are traditionally used in preserving a variety of fermented foods. Inoculated in the food industry as a fermente. Because they play a role in preserving the taste and texture of fermented foods. While the conversion of fermented sugars in raw materials to lactic acid is their main function, the production of antimicrobial peptides, exopolysaccharides and other metabolites is another important feature [9].

8. Functional foods

In many countries today, the role of food in human health and nutrition is very important. So that most of the importance of food, instead of the primary role of food as a source of energy and growth has changed to the biological role of food on functional food. The food production and consumption market has shifted more towards the production of healthy foods. Functional foods are foods that, in addition to their normal nutritional properties, have health benefits for the consumer. They have medicinal value beyond nutritional value and have positive effects on human health. Demand for healthy food products is growing rapidly due to increasing consumer awareness of the benefits of these products. Functional foods include a wide range of dietary supplements, special foods for children, foods enriched with vitamins and minerals, probiotic products, foods containing antioxidants, fiber, protein and soy [8].

8.1 Property of functional foods

The amount of food consumed is important to achieve the beneficial effect of the added nutrient. Identify quality components in the food composition and optimal intake of nutrients in the diet; they reduced diseases and increased the level of health in the human body. In order to achieve the benefits of a healthy food, it must be possible to use it as part of a balanced diet [8]. The gut microflora can face daily challenges such as poor diet, antibiotic use, stress, or food poisoning, leading to an imbalance between “good” and “bad” bacteria. However, eating foods containing probiotics can increase the amount of healthy bacteria in the gut [8]. Probiotics are a group of beneficial microorganisms that, if consumed in sufficient doses of 10⁶ log Cfu/gr, can lead to health.promoting properties in humans [8]. The majority of probiotics belong to the genera Lactobacillus, Bifidobacterium and Lactococcus, which are the natural inhabitants of the large intestine [7, 19]. Their beneficial effects have been extensively studied [4, 20]. Probiotic bacteria can be used in pure culture (as found in supplements) or added to dairy products or other foods. Due to the special conditions that probiotic bacteria need to grow, their survival in most foods will face many problems. One of the methods that can increase the survival of these bacteria and protect them against adverse conditions is the use of encapsulation techniques [13, 21, 22]. This technology refers to a physical and chemical process that inserts the desired bacteria into a coating to produce particles with diameters ranging from a few nanometers to a few micrometers [5]. The purpose of microencapsulation is to create a small environment in which bacteria survive during production and storage and are released in appropriate places (such as the small intestine) in the gastrointestinal tract [21].

9. Microencapsulation of probiotic bacteria

Microencapsulation technologies can be used in many applications in the food industry, such as controlling the oxidative reaction, coating flavors, colors and odors, stable and controlled release of the desired substance, extending the useful life, etc. [5]. Techniques to reduce the lethal effects of the gastrointestinal tract on probiotic microorganisms have been developed and evaluated. Among these, the microencapsulation technique is one of the most appropriate solutions. Microencapsulation is a physicochemical or mechanical process for trapping probiotic bacteria in an emulsion to produce particles with a diameter of a few nanometers to a few millimeters [5].

Technology The microencapsulation of living probiotic cells is covered by other preservatives or mixtures thereof in different techniques [23]. Protection of microcapsules when passing through the stomach can be increased by the use of insoluble wall materials [23]. Microencapsulation protects bacterial cells from environmental pressures such as oxygen, high acidity, and gastric conditions and can be used to pass through the stomach with little damage [24]. In recent years, many studies have been conducted on the preservation of probiotic microorganisms by microencapsulation during food processing and storage [23]. The purpose of microencapsulation is to create an environment in which bacteria survive during processing and storage and are released into, Suitable places the gastrointestinal tract (eg the small intestine) [23].

10. Structure and characteristics of microencapsulation

The first and foremost step in all microencapsulation methods is to select a suitable material as a wall or membrane for the stability and properties of the particles produced in the microencapsulation [25]. These materials are used alone or in combination to form a layer. Covering microencapsulation with a double membrane can act as a barrier against external conditions [26]. The most important choice for the coating material is the Yield of the coatings. The finely coated probiotic in the final product must be degradable and create a boundary between the internal phase and the environment (permeability) and also be evaluation in opinion of cost [4]. The properties of the coating materials and their placement are the main determinants of the functional properties of the microencapsulation [26]. The materials used as coatings for bead can contain two or more layers of base materials [5, 26]. The properties of the coating materials and their shape are the main determinants of the functional properties of the coatings [5]. Microencapsulation must be soluble in water to maintain the coherence of their structure in the food matrix and the digestive tract [5]. Therefore, the materials used as coatings in the microencapsulation should have the following properties. Chemically with the main substance. Ability to form membranes around bacterial cells. Be able to protect bacterial cells against adverse environmental conditions. Be stable and economically viable [26]. To date, there has been no ideal coverage that fits all goals. Therefore, obtaining suitable coatings to create a balance point between the optimal properties, such as protection against moisture, acidity, high temperature, gas exchange (oxygen and carbon dioxide) [26]. The encapsulating agent should not be toxic, as it can directly affect the morphology, diameter and permeability of the particles. Selecting the right material for probiotic microencapsulation is essential for the stability and properties of the particles produced [25]. There is a wide range of natural or synthetic polymers, including: proteins (such as zein, soy protein, collagen, and gelatin), polysaccharides (such as cellulose, starch, alginate, and chitosan), and fats [26].

10.1 Polysaccharide

Polysaccharides are biopolymers composed of monosaccharaides. They have hydroxyl groups that may be intramolecular hydrogen bonded with water or other molecules. They are also influenced by the nature of the monomers of their substituent groups, which alter the molecular and functional properties [26].

10.1.1 Anionic polysaccharides

Alginate, gum Arabic, carrageenan, xanthan, carboxymethylcellulose, gelan are natural anionic polysaccharides that tend to be negative at pH values ​​above pKa. And when they are lower than pKa, they are neutralized [26]. Ionic chemical elements such as Ca ^{+ 2} change the electrical charge properties of all ions. Such as alginate gel, which interacts with opposing groups on the polymer chain [27].

10.1.1.1 Alginate

Alginates are natural marine polysaccharides that are extracted from seaweed [28]. The most important applications of alginate are its stabilizing, gelling and water retaining properties [28]. Alginates are natural polymer chains consisting of 100.3000 monomer units in a chain rigid and somewhat flexible [26]. The ability to connect polymer alginate chains with polyatomic ions such as Ca ^{+ 2}, Ba ^{+ 2}, Sr. ^{+ 2} is through electrostatic bonding and hydrogel formation [26]. When a cation such as Ca ^{+ 2} participates in an interchain bond. It creates a three-dimensional network of gel and micro-and Nano-sized hydrogel bead in the microencapsulation of materials. Which has received much attention in recent studies [26]. One of the benefits of alginate is the formation of gels around bacterial cells. It is also safe and inexpensive. Some of the disadvantages attributed to alginate beads. The resulting beads are highly porous, which reduces the protection of bacterial cells in adverse environmental conditions. Another disadvantage of alginate bead is that it is sensitive to the effects of acid and is not compatible with the resistance of bead in gastric conditions [29, 30]. However, defects can be remedied by combining alginate with other polymer compounds, coating the bead with another compound, or structural modification of alginate using various additives [31].

10.1.1.2 Gum Arabic

Acacia trees are the main source of Gum Arabic. The chemical composition of Gum Arabic is complex and consists of a group of macromolecules composed of a large proportion of carbohydrates (97%) [32]. Gum Arabic (GA) is highly soluble in water and also has a relatively low viscosity compared to other gums [26]. The functional properties of gum Arabic are closely related to its structure, for example, solubility, viscosity, interaction with water and oil in an emulsion, determine the ability of fine coating in Gum Arabic [32]. Some researchers tested Gum Arabic as an indigestible polysaccharide, finding that Gum Arabic reached the large intestine without digestion in the small intestine [33]; Gum Arabic is gradually fermented by the bacterial flora of the large intestine, which produces short-chain fatty acids [34]. Therefore, it can be taken in large daily doses without side effects. Daily consumption of 25 and 30 grams of Gum Arabic for 21 to 30 days reduces total cholesterol by 6 and 10.4%, respectively [32]. Arabic gum is used as a stabilizer, emulsifier and as a coating in the food industry [33]. Solubility and properties of low viscosity emulsions by Gum Arabic enables the ability to retain and transfer the Trapped material in fine encapsulation. Gum Arabic with maltodextrin is a good choice for coating in microencapsulation [35].

10.1.1.3 Carrageenan

Carrageenans are extracted from red seaweed (Rhodophyta) and are composed of various mixtures of sulfated polysaccharides. Carrageenan is a neutral polysaccharide polymer that requires high temperatures to dissolve in large quantities. Potassium chloride is used to preserve and stabilize Carrageenan is a suitable coating material in encapsulation that contain flavorings and aromatic compounds. Forms a brittle, hard gel that melts when heated to low temperatures, forming soft, elastic gels in cold water while carrageenan is soluble. At present, carrageenan has not been widely studied for use in probiotic encapsulation [36, 37]. The properties of carrageenan gel are improved by mixing it with other coating materials such as vegetable oils, calcium alginate, and gums such as xanthan, gelan and locust bean gums by emulsion method [26].

10.1.1.4 Xanthan

Xanthan gum is a microbial exo polysaccharide with a cellulosic structure and a chain of two mannose and a glucuronic acid. They are produced from plant pathogens Sphingomonas elodea and Xanthomonas campestris. Despite its high molecular weight, it dissolves easily in hot and cold water and even in small amounts, it produces a very concentrated solution. as a result of stirring, its viscosity decreases. XG has been shown to be an excellent coating for probiotic microencapsulation, protecting probiotic cells against simulated digestive conditions and high temperatures [26]. Also, XG was successful when used with other coatings such as alginate, chitosan, gelan and cyclodextrin to improve the coating properties of probiotics microencapsulation and increased the viability of microencapsulated probiotics in simulated gastric conditions and intestinal bile salts [26]. Therefore, the addition of chitosan to the alginate-xanthan complex improved the viability of microencapsulation L. plantarum at high temperature and low pH [38]. Other studies using XG in combination with other substances such as protein and alginate improved the survival of Lactobacillus acidophilus in microencapsulation added to yogurt [39].

10.1.1.5 Carboxymethylcellulase

Carboxymethyl cellulose are also called semi-synthetic anionic polysaccharides. The properties of carboxymethylcellulose include; Concentration, adhesion, strength building, water retaining agent, colloidal state, stabilizer, emulsion and layer formation. Due to their diverse properties, they are widely used in the food industry, among them is their use as a coating material in encapsulation of probiotics. In one study, CMC and chitosan were used as coatings for L. acidophilus microencapsulation. They found that the ability of the probiotic to survive during transmission from the simulated gastrointestinal tract was improved [40].

10.1.2 Cationic polysaccharides

Cationic polysaccharides are those that tend to be positive below their pKa value, while remaining much higher than the neutral pKa value. Chitosan is the only naturally Extracted cationic polysaccharide [27]. Other synthetic cationic polysaccharides have been previously described, for example, cation hydroxyethylcellulose and cation hydroxypropyl, that have cosmetic applications [26]. However, despite their potential and benefits as cationic materials, none of them have yet been reported as a coating material for probiotic microencapsulation.

10.1.2.1 Chitosan

Chitosan is a semi-synthetic polymer. Due to its low cost, non-toxicity and adhesion to the outer surface of the particle, it increases the stability of the particles. Which is often used for probiotic microencapsulation [25]. In addition, it provides resistance to the gastrointestinal tract simulator. It has an electrostatic interaction with sodium alginate [10]. The use of chitosan as a capsule for probiotic bacteria can have disadvantages. Because this polysaccharide has an inhibitory effect against microorganisms [25], including lactic acid bacteria [25], Despite the antimicrobial properties of chitosan, it has been used in combination with other encapsulating agents to microencapsulated probiotics [41]. Chitosan coating improves the survival of encapsulated Bifidobacterium longum in the gastrointestinal tract and high temperature [42]. Also, L. rhamnosus ASCC 290 and L. casei ATCC 334 were microencapsulated by alginate-chitosan using extrusion method was observed, 76% microencapsulation efficiency [25].

10.1.3 Non-ionic polysaccharides

Non-ionic polysaccharides are macromolecules that have no formal charge. However, other neighboring species and / or environmental conditions may affect their loading characteristics Natural, non-ionic polysaccharides such as starch, maltodextrins, cyclodextrins and guar gum have been used as coatings for probiotic microencapsulation [43].

10.1.3.1 Starch

Starch is produced by plants and is mostly composed of two different polysaccharides of D-glucose: linear and spiral amylose and highly branched amylopectin. Starch due to its high amylose leads to the formation of flexible and strong coatings. Corn starch is also known as resistant starch (RS) due to its high amylose content, which is the most common type of starch [44]. Starch films are: odorless, tasteless, colorless, non-toxic and semi-permeable to carbon dioxide, moisture, oxygen as well as fat and flavoring components [44]. Modified starch such as (actinyl-succinate starch) is a food additive. It was successfully optimized as a coating material for microencapsulation of Bifidobacterium by spray drying method. Actinyl-succinate starch is preferred because it is suitable for spray drying.

10.1.3.2 Maltodextrin

Maltodextrins H2o {(c6H10o5) n} starch is hydrolyzed. It is a natural, non-ionic polysaccharide that binds glucose units together mainly by glycoside bonds (4 → 1). Its macromolecules do not have a specific charge [26]. Unlike starch, they have high solubility and low viscosity in the formation of encapsulation, moisture control, reduced wall permeability to oxygen, reduced adhesion problems, easy digestibility and easy drying are the properties of gel formation in maltodextrin [26]. Equivalent dextrose (DE) indicates the reduced number of aldehyde groups relative to pure glucose (constant concentration), so that high DE indicates lower weight, higher solubility. Due to having a hydrophilic group, it increases the moisture in the final product. Due to their low cost, neutral flavor and aroma, as well as their role in protecting bacterial cells, resistant to thermal degradation during drying, maltodextrins are used as Coating material in encapsulation [26, 45]. In general, in maltodextrins, the solubility and stability dependence of the high molecular mass and the viscosity, adhesion, and crystallization depend on the low molecular weight [35].

10.1.3.3 Guar gum

Guar gum is structurally a type of polysaccharide whose main chain is mannose and the sidelong groups attached to it are galactose. This substance is extracted from Guar plant and in combination with water, creates a concentrated solution, and due to this property has many applications in the food industry. According to the US Food and Drug Administration, the use of appropriate amounts of guar gum in various food products is safe. It has recently been described as a coating agent for probiotic encapsulation. Amita et al. [46] found that a mixture of fructooligosaccharide and guar gum improved the viability of microencapsulation probiotics in a simulated gastrointestinal tract during heat treatment. In another study by Muzzafar et al. On the bacteria L. acidophilus, L. rhamnosus and B. longum with guar gum and xanthan gum, they observed an improvement in probiotic survival in the preparation of cream biscuits [47]. Recent studies have found that microencapsulation of Lactobacillus by alginate and guar gum coatings increased the viability of chocolate milk, and that microencapsulation had no effect on the flavor of the final product.

10.1.3.4 Cyclodextrin

Cyclodextrins are annular oligosaccharides containing glucose units with alpha 1 and 4 glucopyranose bonds. Cyclodextrins are produced through starch by enzymatic conversion. The spatial structure of cyclodextrin forms a hydrophilic surface and a hydrophobic cavity. Its benefits include the ability to remove cholesterol from many foods (eg eggs and dairy); inhibits the increase of plasma cholesterol and triacylglycerol [26]. Cyclodextrin coatings are also used more for controlled release in drugs [48]. Therefore, not many studies have been performed on encapsulation of probiotics. In recent studies, microencapsulation of Saccharomyces boulardii, L. acidophilus, and Bifidobacterium bifidum by cyclodextrin and gum arabic increased survival in gastric and intestinal cloning conditions and thermal resistance compared to free cells [26].

10.2 Lipids

Lipids are made up of fats, fatty acids, waxes and phospholipids. Lipids are used as coatings in microencapsulation. Due to their relatively low polarity, they prevent moisture transfer. The hydrophobicity of lipids makes the microencapsulation coatings brittle [49]. Therefore, lipids are combined with other coatings such as proteins and polysaccharides to improve the microencapsulation properties. In previous reports, polysaccharide coatings and proteins have been found to cause structural cohesion and selective permeability to gases (so2, o2) [50]. The addition of fat also made the coatings resistant to water vapor. Most lipid coatings are fats: their source-dependent fats include vegetable and animal fats. The chemical structure of fats is composed of fatty acids and glycerol. Hence, their properties largely depend on the composition of fatty acids. Vegetable fats are widely used as concurrent encapsulation materials in microencapsulation of probiotics by method emulsification or by spry drying [26]. Silva et al., On the other hand, microencapsulated probiotics using vegetable oil as a coating alone or covered with gum Arabic and gelatin. Microencapsulated bacteria showed greater protection than free bacteria in simulated gastrointestinal conditions (eg, pH, temperature, sodium chloride, and sucrose) [51].

Waxes are GRAS materials and have been widely used in the food industry, for example as food additives or as a protective coating for fruits, vegetables and cheese. Nevertheless, waxes are less commonly used as coatings for microencapsulation probiotics. For example, Mandal et al. [52] reported the use of wax, stearic acid, or poly-L-lysine as the outer coating of probiotic microcapsules prepared with resistant starch and alginate, that wax and stearic acid showed improved survival of L. casei encapsulated probiotic cells under simulated gastrointestinal conditions. In particular, stearic acid coatings provide better protection. Contrary to the results of the previous study, Rao et al. [53], evaluated the use of wax or stearic acid as the outer coating of probiotic microcapsules prepared with cellulose acetate phthalate (CAP). They found that wax-coated microcapsules the highest survival rate of Bifidobacterium pseudolongum in simulated gastric juice.

Phospholipids are a large group of lipids commonly used in the food industry and have the ability to form emulsions, micelles and liposomes. These lipids contain phosphorus and play an important role in the construction and metabolism of living cells. Phospholipids are more complex than simple lipids (fats and waxes). Examples of phospholipids are phosphatidic acid (phosphatidate) (PA), phosphatidyl ethanolamine (cephalin) (PE), phosphatidylcholine (PC) and phosphatidylserine (PS). In this regard, phospholipids are the main components of liposomes. When phospholipids are dispersed in water, the molecules come together to form a distinct bilayer. Such interactions cause the formation of vesicles, also called liposomes [53]. Liposomes have been used extensively as systems to transport active compounds such as drugs, vitamins, enzymes, and so on.

Although liposomes have shown great potential for controlled encapsulation and release of nutrients, their use in food has not yet been fully utilized [26]. Despite the high potential of liposomes for encapsulation and controlled release of nutrients, their use in food has not yet been fully utilized [26]. For example, up to now, microencapsulation of probiotics by liposomes has not been reported, which may be due to the cost of the process and materials as well as the large size of the probiotic microorganisms [54]. However, the resistance of liposomes to the gastrointestinal tract as well as the survival of probiotics in the intestinal there are issues that need to be review.

10.3 Protein

Proteins are excellent materials for microencapsulation of probiotics; however, they are often used in combination with other coating agents. To date, few proteins have been used as coatings [26]. Due to their properties, many proteins are used as a good barrier against O2 permeability and CO2 as a coating agent. Each protein has a unique set of physicochemical properties [55]. Proteins used as coating agents for probiotic microcapsules, on their nature, can be classified as plant or animal proteins based. Examples of animal origin proteins include gelatin, casein, whey protein concentrate (WPC), whey protein isolate (WPI), egg whites, and caseinates. Examples of plant origin proteins, on the other hand, include corn (saddle), pea, wheat, and soy. Gelatin is one of the oldest and most widely used proteins in the food industry, as an ideal coating material in the preparation of microencapsulation in probiotics [56]. Recent studies have shown that gelatin provides a suitable coating by interacting with a wide range of polysaccharides in a variety of ways [26].

Some of the other proteins used in probiotic microencapsulation are egg white (albumin), soy protein and whey protein. These proteins have good emulsifying and gelling properties that are considered as ideal materials for microencapsulation [26]. In the study, soy protein isolates and alginate were used as a coating material for microencapsulation of L. plantarum and L. acidophilus by spray drying. Also in the study, Pitigraisorn et al. Used egg albumin coatings and stearic acid to protect L. acidophilus by electro spraying and fluidized bed drying [57]. Soy plant protein isolate is suitable in the microencapsulation of probiotics, for vegetarians and Milk sensitive people, which is a source of high quality proteins [58]. The synergistic effects of soy protein isolate with other nutrients enhance the final properties of microcapsule coatings. In addition, previous studies have found that the jelly properties of soy protein isolate are deformed in the presence of CaSO4, MgCl2 or MgSO4. And can be useful for future applications in the food industry, including the microencapsulation process [26]. Sodium caseinate (SC) is the most common form of casein, which is used as a suitable coating material in microencapsulation due to its physicochemical properties, increased denaturation and heat resistance.

Whey proteins in concentrate (WPC) and isolated (WPI) contain 35%. 85% and > 95% protein, respectively. WPCs are low in fat and cholesterol and high in lactose and total fats, while WPIs are high in protein and low in lactose and fat [59]. Whey proteins, in its various forms, have recently been studied as coatings for microencapsulation of probiotics [26]. In some studies, it has been shown that the ability and elasticity and strength of the gel increase in the presence of the main components of whey protein (beta-lactoglobin and alpha-lactoalbumin).

Sweet whey (SW) is an example of a product that contains casein and whey proteins. In recent studies, sweet whey was used to microencapsulation B. lactis with spray dryer method [60].

11. Microencapsulation of methods

Microencapsulation methods for encapsulate bioactive compounds have been proposed in several ways. To increase their ability release and stability under conditions product process and storage [26]. The attention of the food industry to the low cost of the method used is also worth considering. However, the final quality of the product should not be affected. The method used in forming the beads affects indicators such as the diameter and moisture of the beads [26]. Successful methods used in microencapsulating such as spray drying, spray freeze drying, electro spraying, fluidized bed drying; extrusion, Emulsification and coacervation [26].

11.1 Fluidized bed drying

Fluidized bed technology was patented by Dr. Wurster et al. And developed between 1957 and 1966 [5]. Proper air circulation in the atomic nozzle ensures that all particles in the fluidized bed achieve a uniform coating. This nozzle atomizes the selected coating (an aqueous solution) at low temperature by evaporating the solid solvent [5]. Air turbulence allows the coated particles to be suspended and coated evenly. The wall materials used in this method include cellulose derivatives, dextrin, emulsifiers, lipids, protein derivatives and starch which is used dissolved in an evaporative solvent. Fluidized bed technology is suitable for microencapsulation probiotic bacteria using cell layering with various preservatives such as glucose, maltodextrin, trehalose or sucrose, preferably skim milk to improve bacterial dehydration [5]. Recent studies have shown the effectiveness of fluidized bed drying for probiotic microencapsulation [25, 26].

11.2 Freeze drying

This method of drying is called lyophilization. In this method, probiotics are frozen in the presence of a coating material. It works by reducing the ambient pressure and creating a vacuum at low temperatures to sublimate frozen water directly. The most common uses of wall materials include proteins, maltodextrins, disaccharides, and gums. One of the most important benefits of freeze drying is water phase conversion and prevention of oxidation. It has the highest survival rate after drying and the lowest loss during storage. In any case, freeze-drying is a very expensive technology. Therefore, in further studies, spray drying [61], is used to dry probiotics. The freeze drying process provides maximum stability during storage. For this reason, this technique is used as a second method during microencapsulation. In this way, the stability of probiotic bacteria can be improved in the gastrointestinal tract and the beneficial effect of probiotic [45].

11.3 Spray drying

Spray drying is a common method for producing microencapsulation in food because it has been proven to be suitable for large-scale industrial applications [62]. The first spray dryer was made in 1878 and is therefore a relatively old method compared to rival technologies [62]. This is probably the most economical and effective drying method in the industry, first used to preserve a flavor in the decade of 1930. However, the industrial production of encapsulated probiotics using hot air dryers is not very useful in food, due to the reduced viability when bacteria dry and the reduced stability during storage. The bacterial cell is transferred to an emulsion that acts as a microencapsulation. The encapsulate is usually a hydrocolloid such as gelatin, vegetable gum, modified starch, dextrin or non-gelling protein. The resulting solution dries and acts as a barrier to oxygen and aggressive substances. In the spray drying process, a liquid mixture in a container with a single-fluid nozzle, a two-liquid nozzle is atomized, and the solvent is evaporated by contact with hot air [62].

11.4 Extrusion

It is a physical method of trapping probiotic living cells and uses hydrocolloids (alginates and carrageenan) as encapsulates. Tiny droplets from inside a nozzle device under air pressure or a syringe, dropped out inside a hardening solution such as calcium. Extrusion is a simple and inexpensive method that uses a gentle operation. It does not damage probiotic cells and increases the survival of probiotic bacteria. This technology does not contain harmful solvents and can be done under aerobic and anaerobic conditions. The most important disadvantage of this method is that due to the slow formation of bead, it is very difficult to use in industry [63]. Gel granules can be added to a second polymer solution as a coating. The second layer is used to protect the cell or improve the organoleptic properties of the cell [63].

11.5 Emulsion

It is a chemical technique for trapping probiotic cells. Most hydrocolloids (alginate, carrageenan and pectin) are used as encapsulates. An emulsifier and a surfactant are needed to form the bead. A hardening solution such as calcium chloride is then added to the emulsion [63]. Its main disadvantage is the large diameter of the bead.

11.6 Electro spraying

The electrospray technology used for microencapsulation is based on the principle of electro-hydrodynamics. This process includes a high voltage electric field. Which enters capillary liquid containing the main substance and is sprayed where the spherical droplets precipitates. Freezing occurs through various methods, for example by chemical hardening or by solvent evaporation. This method is combined with other microencapsulation techniques to increase the microencapsulation efficiency. So far, the electrospray extrusion technique has been used successfully for probiotic microencapsulation [64].

11.7 Coacervation

Drops are rich in organic matter that are formed through the separation of the liquid phase. It is mainly due to the association of oppositely charged molecules (polyelectrolytes, polysaccharides) or hydrophobic proteins (elastin polypeptides) [65]. A phenomenon produced by the accumulation of colloidal droplets that causes the simultaneous separation of two liquid phases. A dense phase is rich in polymer and a very dilute phase. Particle diameters range from 1 to 100 micrometers [65].

12. Application of microencapsulation bacteria

The efficiency of microencapsulated bacteria can be evaluated from different angles. Such as increasing the survival of probiotics, increasing the resistance of microcapsules to bacteriophage invasion, increasing their resistance to toxic and lethal chemical agents, as well as the ability to produce probiotic foods by improving the survival and stability of probiotic cells during production, storage and passage of the digestive system-Finally, it preserves the sensory properties of the product, which contains microencapsulation bacteria [23, 66].

13. Adding probiotic microencapsulation to food products

Dairy products have traditionally been the best producer of probiotics. They showed excellent conditions for the survival of probiotic bacteria. Because milk has a physicochemical composition rich in protein and with a significant amount of lipids. As a result, it creates a protective matrix for probiotics [23]. Microencapsulation is important to increase probiotic The addition of bead should not affect the sensory properties of food products. The addition of bead should not affect the sensory properties of food products [63]. Most of the research has been done and the products that are marketed in the food industry as probiotics. Dairy products are probiotics. Due to the problems of lactose intolerance in some people in the community (about 70% in Asia), sensitivity to milk proteins and the prevalence of high cholesterol require foods other than dairy that are good carriers for probiotic bacteria. Non-dairy foods provide a variety of substrates of antioxidants, dietary fiber, minerals, and vitamins [23]. The development of non-dairy probiotic products such as fruits, vegetables and grains has been shown to be one of the best choices and has increased the demand for non-dairy probiotics [23]. Properties and structural compounds (nutrients such as minerals, vitamins, dietary fiber and antioxidants, including the right amount of sugar) Fruits, vegetables and grains are suitable and ideal substrates for probiotic microbes [67]. Various factors such as protein concentration, sugar, fat and pH level in the food product can affect the growth and survival of probiotics [63].

14. Release of probiotic bacteria from microencapsulation

Scientific sources related to the probiotic microencapsulation emphasize on its destruction, in the large intestine. The microencapsulated bacteria can resist acidic conditions in the stomach. Depending on the processing conditions and the type of coated material used, it regulates the release rate of microencapsulation bacteria in the presence of bile salts [5]. In this way, probiotic bacteria are protected and as a result, high concentrations of living cells can be achieved [5]. The finely coated must have selective permeability to support the environmental conditions that keep cells live, so that it can be designed to release probiotic cells in a specific area of ​​the body [5].